Forklift forks need to be inspected regularly because like anything else made from metal, they wear out. If you drag your forks on concrete, they will wear out. If the previous driver lifted too much, they might be bent.
OSHA requirement is for a daily checklist of forklift forks so I am sure same applies to tractors.
More forklift fork technical stuff here http://store.intellaliftparts.com/FAQS.html